SYSTEM REVIEW OF THE MODIFIED LIGHT DUTY UTILITY ARM AFTER THE COMPLETION OF THE NUCLEAR WASTE REMOVAL FROM SEVEN UNDERGROUND STORAGE TANKS AT OAK RIDGE NATIONAL LABORATORY

摘要

The Modified Light Duty Utility Arm (MLDUA) is a custom seven-degree-of-freedom long-reach manipulator system developed, designed, and built by SPAR Aerospace, Ltd. The MLDUA was delivered to Oak Ridge National Laboratory (ORNL) in November 1996. After operational tests and training cold tests, the MLDUA was moved to the first underground tank (W-3) in May 1997. After the completion of tank W-3, the MLDUA was used in cleanup operations of six other underground tanks, in this order, tanks W-4, W-6, W-7, W-10, W-8, and finally on tank W-9. Tank W-9 was completed in September 2000. Tanks W-3 and W-4 are 25-foot diameter tanks and the other five tanks are 50-foot diameter tanks. The MLDUA was deployed only in one tank riser for the 25-foot tanks. For the 50-foot tanks, the MLDUA was deployed in either two or four tank risers. The MLDUA performed the following types of operations in support of the underground tank waste cleanup operations: grasping the sluicer to allow deployment of the Hose Management Arm (HMA) into the tanks, holding and maneuvering the sluicer to remove tank water and waste material, tank wall radiation surveys, tank wall material sample collection, tank wall cleaning operations with high-pressure water jets, vertical pipe cutting operations, pipe plugging operations and support for tank wall coring operations. The MLDUA performed exceptionally well considering it is a one-of-a-kind long-reach manipulator prototype design. The MLDUA operations included over 7400 hours of in-tank exposure to radiation fields with an estimated total dose of 77,000 rads. Total working time within the tanks was over 2250 hours. While the MLDUA performed exceptionally well, a relatively few problems developed during tank cleanup operations. The most serious problem that developed during operations was the loss of the manipulator's wrist roll operation. The wrist roll drive motor's power supply cable developed an internal short within the manipulator's umbilical cable during operations on tank W-6. The MLDUA operators compensated for operations without an operating wrist roll by pre-planning the MLDUA jobs and presetting the wrist position. The MLDUA was never a delay in tank operations. Also, many "lessons" were learned in both manipulator operations within the tanks and manipulator design. Many design modifications were identified that would have made the MLDUA a better machine. The design modifications include changes to make setup and take down of the MLDUA easier, to perform maintenance easier, reduce operator's radiation exposure during MLDUA support operations within the Tank Riser Interface Containment (TRIC), and the Operator's computer graphic interface. Overall, the MLDUA performed exceptionally well and has a proven track record.